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<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        /*  当分数高于90时打印A
 
          否则如果当分数高于80时打印B
          
          否则如果当分数高于70时打印C
          
          否则如果当分数高于60时打印D
          
          其他情况就打印E
        */
        var grade = prompt('输入分数:');
        if (grade >= 90) {
            alert('A');
        } else if (grade >= 80) {
            alert('B');
        } else if (grade >= 70) {
            alert('C');
        } else if (grade >= 60) {
            alert('D');
        } else {
            alert('E');
        }




    </script>
</head>

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</body>

</html>